CMOS Off-Chip Drivers Having Short-Circuit Protection
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Output short-circuit protection of a high-power CMOS off-chip driver (OCD) is provided by a feedback network which cuts off the output stage of the OCD after a time delay when its output is externally shorted to ground or otherwise incorrectly terminated. In normal operation, the output voltage is in phase with the input voltage and with the voltage controlling the feedback protection circuitry. When the output is shorted to ground, the feedback network forces the control voltage to the output stage to reverse polarity to turn off the stage. Circuit parameters are adjusted for a race condition which may arise during normal operation. Referring to the figure, transistor devices (T1, T'1), (T2, T'2), (T3, T'3), and (T4, T'4) are inverters forming a driver chain to enhance the driving capability of the OCD.